Recording medium

ABSTRACT

A recording medium includes a base, a second ink-receiving layer, and a first ink-receiving layer in this order. The first ink-receiving layer contains gas-phase method silica, a binder, a cationic polymer having a sulfonyl group, and glycol. The second ink-receiving layer contains gas-phase method silica and a binder and (1) does not contain any cationic polymer having a sulfonyl group or (2) contains a cationic polymer having a sulfonyl group in an amount not higher than 0.1 parts by mass based on 100 parts by mass of the gas-phase method silica.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a recording medium.

2. Description of the Related Art

Silica can form a porous structure showing high ink-absorbing propertiesand is therefore suitable as inorganic particles that are used in theink-receiving layer of a recording medium. In general, silica is roughlyclassified based on the production process into wet method and drymethod (gas-phase method). In particular, the silica prepared by the drymethod (gas-phase method) (hereinafter, also referred to as “gas-phasemethod silica”) has a particularly large specific surface area andthereby shows particularly high ink-absorbing properties. In addition,the silica has a low refractive index and thereby makes the transparencyof the ink-receiving layer high to give good color development of animage.

Japanese Patent Laid-Open No. 2001-341418 discloses a method ofenhancing the ozone resistance of an image by a recording medium havingan ink-receiving layer containing such gas-phase method silica. ThisPatent Literature describes an improvement in the ozone resistance of animage by an ink-receiving layer containing an amino compound havingrepeating alkylene oxide groups and a diallylamine hydrochloride-sulfurdioxide copolymer as a cationic polymer, in addition to gas-phase methodsilica and polyvinyl alcohol as a binder.

Japanese Patent Laid-Open Nos. 2005-280035 and 2004-262232 describeimprovements in the bleed resistance and color development of an imageby a recording medium having an ink-receiving layer prepared bylaminating a finish coat layer containing a cationic polymer on anundercoat layer containing a pigment and a binder.

However, according to the investigation by the present inventors, thoughthe ozone resistance of an image is improved in the recording mediumdescribed in Japanese Patent Laid-Open No. 2001-341418, cracking occursin the ink-receiving layer. In Japanese Patent Laid-Open No.2005-280035, since gas-phase method silica is not used, the intendedcolor development of an image is not obtained. In Japanese PatentLaid-Open No. 2004-262232, though gas-phase method silica is used, abronze phenomenon occurs in the resulting image.

SUMMARY OF THE INVENTION

The present invention provides a recording medium, in which cracking ofthe ink-receiving layer thereof is prevented from occurring, the ozoneresistance of a resulting image is high, and a bronze phenomenon issuppressed.

The recording medium according to the present invention includes a base,a second ink-receiving layer, and a first ink-receiving layer in thisorder, wherein the first ink-receiving layer contains gas-phase methodsilica, a binder, a cationic polymer having a sulfonyl group, andglycol; and the second ink-receiving layer contains gas-phase methodsilica and a binder and does not contain (1) any cationic polymer havinga sulfonyl group or contains (2) a considerably small amount of acationic polymer having a sulfonyl group, i.e., in an amount not higherthan 0.1 parts by mass based on 100 parts by mass of the gas-phasemethod silica.

According to the present invention, a recording medium, in whichcracking of the ink-receiving layers thereof is prevented fromoccurring, the ozone resistance of a resulting image is high, and abronze phenomenon is suppressed, is provided.

Further features of the present invention will become apparent from thefollowing description of exemplary embodiments with reference to theattached drawing.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram illustrating an example of the structureof a recording medium according to the present invention.

DESCRIPTION OF THE EMBODIMENTS

The present invention will now be described in detail by embodiments.The present inventors investigated various compounds and have found thatthe ozone resistance of an image is improved by an ink-receiving layercontaining a cationic polymer having a sulfonyl group. This is believedto be caused by that in the cationic polymer having a sulfonyl group;the electron density of the cationic groups is reduced due to theelectron-withdrawing sulfonyl group to strengthen the association withthe coloring material. However, it was revealed that the cationicpolymer having a sulfonyl group decreases the viscosity of coatingsolution to readily cause cracking in the ink-receiving layer in dryingthereof. Accordingly, the present inventors have performed investigationand have revealed that the cracking of the ink-receiving layer isinhibited and the ozone resistance of an image is enhanced in thestructure of the present invention, that is, when the ink-receivinglayer includes a second ink-receiving layer (hereinafter, also simplyreferred to as “second layer”) and a first ink-receiving layer(hereinafter, also referred to as “first layer”) in this order from thebase side; the first layer contains a cationic polymer having a sulfonylgroup; and the second layer does not contain (1) any cationic polymerhaving a sulfonyl group or contains (2) a considerably small amount of acationic polymer having a sulfonyl group, i.e., in an amount not higherthan 0.1 parts by mass based on 100 parts by mass of gas-phase methodsilica. Furthermore, the first layer contains glycol and therebyprevents a bronze phenomenon from being readily caused by the cationicpolymer having a sulfonyl group.

Recording Medium

Each component constituting the recording medium of the presentinvention will now be described.

Ink-Receiving Layer

The ink-receiving layer of the recording medium according to the presentinvention contains gas-phase method silica and a binder and is composedof a second layer not containing any cationic polymer having a sulfonylgroup and a first layer containing a cationic polymer having a sulfonylgroup in this order from the base side. The structure of theink-receiving layer according to the present invention will be describedwith reference to FIG. 1. In FIG. 1, the reference sign (a) denotes thebase, the reference sign (b) denotes the second layer, and the referencesign (c) denotes the first layer. In the present invention, anotherlayer may be disposed on the first layer and/or between the first layerand the second layer.

In the present invention, the thickness of the ink-receiving layer (thetotal thickness of layers (b) and (c) in FIG. 1) can be 20 μm or moreand 50 μm or less, in particular, 30 μm or more and 45 μm or less, fromthe viewpoint of the ink-absorbing properties. The thickness of theink-receiving layer is determined by measuring thicknesses of at leastfive points of a cross section of the recording medium with a scanningelectron microscope (SEM) and calculating the average thereof.

First Layer

In the present invention, the first layer of the ink-receiving layercontains a cationic polymer having a sulfonyl group. The thickness ofthe first layer (the thickness of layer (c) in FIG. 1) can be 5 μm ormore and 30 μm or less, in particular, 10 μm or more and 25 μm or less.When the thickness of the first layer is smaller than 10 μm, the effectof improving the ozone resistance of an image may be insufficient, andwhen the thickness is larger than 25 μm, the effect of inhibitingoccurrence of cracking of the ink-receiving layer may be insufficient.

In the present invention, the first layer can be present within 5 μmfrom the outermost surface of the ink-receiving layer, from theviewpoint of improving the ozone resistance of an image.

Second Layer

In the present invention, the second layer of the ink-receiving layerdoes not contain (1) any cationic polymer having a sulfonyl group orcontains (2) a considerably small amount of a cationic polymer having asulfonyl group, i.e., in an amount not higher than 0.1 parts by massbased on 100 parts by mass of the gas-phase method silica. The thicknessof the second layer (the thickness of layer (b) in FIG. 1) can be 10 μmor more and 35 μm or less from the viewpoint of inhibiting occurrence ofcracking of the ink-receiving layer. In the present invention, all ofthe layers of the ink-receiving layer other than the first layer mayhave the same structure as that of the second layer.

Each component constituting the ink-receiving layer will now bedescribed.

Gas-Phase Method Silica

In the present invention, the ink-receiving layer contains gas-phasemethod silica in both the first layer and the second layer. Thegas-phase method silica can be prepared by, for example, preparation ofanhydrous silica by high-temperature gas-phase hydrolysis of halogenatedsilicon (flame hydrolysis) or by thermal reduction-vaporization ofsilica sand and coke through arcing in an electric furnace and oxidationthe resulting product with air (arc process). Specific examples of thegas-phase method silica include Aerosil (manufactured by Nippon AerosilCo., Ltd.) and Reolosil QS type (manufactured by Tokuyama Corporation).

In the present invention, the gas-phase method silica can have aspecific surface area (by the BET method) of 50 m²/g or more and 400m²/g or less, in particular, 200 m²/g or more and 350 m²/g or less.

In the present invention, the content (mass %) of the gas-phase methodsilica in the ink-receiving layer can be 50 mass % or more and 98 mass %or less, in particular, 70 mass % or more and 96 mass % or less.

In the present invention, the application amount (g/m²) of the gas-phasemethod silica in the formation of the ink-receiving layer can be 8 g/m²or more, in particular, 10 g/m² or more and 30 g/m² or less. Anapplication amount of less than 10 g/m² may provide insufficientink-absorbing properties, and an application amount of higher than 30g/m² may cause cracking during drying in the production of a recordingmedium.

In the present invention, the gas-phase method silica can have anaverage primary particle diameter of 1 nm or more and 1 μm or less, inparticular, 30 nm or less. The average primary particle diameter can be3 nm or more and 10 nm or less. In the present invention, the averageprimary particle diameter of the gas-phase method silica is thenumber-average particle diameter of the diameters of circles having thesame areas as projected areas of primary particles of the gas-phasemethod silica observed by an electron microscope. On this occasion, themeasurement is performed for at least 100 points.

Binder

In the present invention, the ink-receiving layer contains a binder inboth the first layer and the second layer. The binder may be anymaterial that can bind the gas-phase method silica and can form a coatand does not impair the effects of the present invention.

Examples of the binder include starch derivatives such as oxidizedstarch, esterified starch, and phosphorylated starch; cellulosederivatives such as carboxymethyl cellulose and hydroxyethyl cellulose;casein, gelatin, soybean protein, polyvinyl alcohol (PVA), andderivatives thereof; various polymers such as polyvinylpyrrolidone andmaleic anhydride resins and conjugated polymer latex such asstyrene-butadiene copolymers and methyl methacrylate-butadienecopolymers; acrylic polymer latex such as polymers of acrylate andmethacrylate; vinyl polymer latex such as ethylene-vinyl acetatecopolymers; functional group-modified polymer latex of theabove-mentioned various polymers of monomers containing functionalgroups such as carboxyl groups; the above-mentioned polymers cationizedwith cationic groups and the above-mentioned polymers of which surfacesare cationized with cationic surfactants; the above-mentioned polymerspolymerized in the presence of cationic polyvinyl alcohol so as todistribute the polyvinyl alcohol on the polymer surfaces; theabove-mentioned polymers polymerized in a suspension/dispersion ofcationic colloidal particles so as to distribute the cationic colloidalparticles on the polymer surfaces; aqueous binders such as thermosettingsynthetic resins, e.g., melamine resins and urea resins; polymer andcopolymer resins of methacrylate and acrylate such as poly(methylmethacrylate); and synthetic resin binders such as polyurethane resins,unsaturated polyester resins, vinyl chloride-vinyl acetate copolymers,polyvinyl butyral, and alkyd resins. These binders may be used alone orin a combination of two or more thereof, as necessary.

Among the above-mentioned binders, polyvinyl alcohol (PVA) and polyvinylalcohol derivatives can be particularly used. Examples of the polyvinylalcohol derivative include cation-modified polyvinyl alcohol,anion-modified polyvinyl alcohol, silanol-modified polyvinyl alcohol,and polyvinyl acetal. The PVA can be synthesized by hydrolysis(saponification) of polyvinyl acetate. The degree of saponification ofthe PVA can be 80 mol % or more and 100 mol % or less, in particular, 85mol % or more and 100 mol % or less. The degree of saponification is theratio of the molar number of hydroxyl groups generated by saponificationof polyvinyl acetate to polyvinyl alcohol, and is a value measured bythe method described in JIS-K6726. In addition, the PVA can have anaverage polymerization degree of 1500 or more, in particular, 2000 ormore and 5000 or less. Incidentally, the average polymerization degreeherein is the average polymerization degree determined by the methoddescribed in JIS-K6726 (1994).

In the present invention, the content of the gas-phase method silicacontained in the ink-receiving layer of the recording medium can bethree to twenty times the content of the binder, in terms of mass ratio.

Crosslinking Agent

In the present invention, the ink-receiving layer may contain acrosslinking agent. Examples of the crosslinking agent include aldehydecompounds, melamine compounds, isocyanate compounds, zirconiumcompounds, amide compounds, aluminum compounds, boric acids, and boricacid salts. These crosslinking agents can be used alone or in acombination of two or more thereof, as necessary. Among theabove-mentioned crosslinking agents, boric acids and boric acid saltshave a notable effect of inhibiting cracking of the ink-receiving layerand can be particularly used.

Examples of the boric acid include orthoboric acid (H₃BO₃), metaboricacid, and diboric acid. The boric acid salt can be any of water-solublesalts of these boric acids, and examples of the boric acid salt includealkali metal salts of boric acids such as sodium salts and potassiumsalts of boric acids; alkaline earth metal salts of boric acids such asmagnesium salts and calcium salts of boric acids; and ammonium salts ofboric acids. Among these boric acids and boric acid salts, orthoboricacid has notable effects of stabilizing the coating solution for a longtime and inhibiting cracking and can be particularly used.

The amount of the boric acid or boric acid salt can be appropriatelyselected depending on, for example, the production conditions. Thecontent of the boric acid or boric acid salt can be 5.0 mass % or moreand 50.0 mass % or less relative to the content of the binder containedin the ink-receiving layer.

Cationic Polymer Having a Sulfonyl Group

In the present invention, the first layer of the ink-receiving layercontains a cationic polymer having a sulfonyl group. The cationicpolymer having a sulfonyl group can be prepared by copolymerization of acationic monomer, such as diallylamine hydrochloride, methyldiallylaminehydrochloride, or diallyldimethylammonium chloride, with sulfur dioxide.Specific examples of the cationic polymer having a sulfonyl groupinclude compounds represented by the following Formula (1) and compoundsrepresented by the following Formula (2):

(in Formulae (1) and (2), R₁ and R₂ each represent a hydrogen atom or analkyl group, provided that R₁ and R₂ are not simultaneously hydrogenatoms; X⁻ represents a halogen ion, a sulfate ion, a sulfonate ion, analkylsulfonate ion, an acetate ion, an alkylcarboxylate ion, or aphosphate ion; and n is an integer).

Examples of the compound represented by Formula (1) or (2) includediallylamine hydrochloride-sulfur dioxide copolymer PAS-92,methyldiallylamine hydrochloride-sulfur dioxide copolymer PAS-2201CL,and diallyldimethylammonium chloride-sulfur dioxide copolymer PAS-A-5(these are manufactured by manufactured by Nittobo Medical Co., Ltd.).In the present invention, the compounds represented by Formula (1) canbe particularly used. Furthermore, PAS-2201CL and PAS-A-5 are superiorto PAS-92 in the effect of inhibiting the heat-induced yellowing of therecording medium.

The amount of the cationic polymer having a sulfonyl group contained inthe first layer of the ink-receiving layer can be 0.2 parts by mass ormore and 4.0 parts by mass or less, in particular, 0.5 parts by mass ormore and 2.0 parts by mass or less, based on 100 parts by mass of thegas-phase method silica. Within this range, both the effect of improvingthe ozone resistance of an image and the effect of inhibiting crackingof the ink-receiving layer can be achieved at high levels.

Glycol

In the present invention, the term “glycol” refers to a compound havinga structure in which a hydroxyl group is substituted on each of twocarbon atoms of a linear or cyclic aliphatic hydrocarbon. Specificexamples of the glycol include ethylene glycol, diethylene glycol,triethylene glycol, propylene glycol, dipropylene glycol, isopreneglycol, hexylene glycol, 1,3-butylene glycol, and 1,2-hexanediol.

The amount of the glycol contained in the first layer of theink-receiving layer can be 2.0 parts by mass or more and 20.0 parts bymass or less based on 100 parts by mass of the cationic polymer having asulfonyl group. In addition, the amount of the glycol contained in thefirst layer of the ink-receiving layer can be 2.0 parts by mass or moreand 20.0 parts by mass or less, in particular, 5.0 parts by mass or moreand 15.0 parts by mass or less, based on 100 parts by mass of thegas-phase method silica.

Polyvalent Metal

In the present invention, the ink-receiving layer can contain apolyvalent metal. In the present invention, the “polyvalent metal”includes the polyvalent metal in its ion form and the polyvalent metalin its salt form. Examples of the polyvalent metal include di- or morevalent metals. Examples of the divalent metal include alkaline earthmetals such as beryllium, magnesium, calcium, strontium, barium,zirconium, and radium. Examples of the trivalent metal include aluminum,yttrium, zirconium, iron, and other transition metals. In the presentinvention, such a polyvalent metal can be added to the coating solutionfor ink-receiving layer in a water-soluble salt form such as ahydroxide, a chloride, or a nitrate. Incidentally, in the presentinvention, the term “water-soluble” refers to that the solubility inwater under ordinary temperature and ordinary pressure is 1 mass % ormore.

In the present invention, among the water-soluble salts of theabove-mentioned polyvalent metals, water-soluble salts of zirconium andaluminum can be particularly used. Specific examples of thewater-soluble salts of zirconium include zirconium acetate, zirconiumchloride, zirconium oxychloride, zirconium hydroxychloride, zirconiumnitrate, basic zirconium carbonate, zirconium hydroxide, zirconiumammonium carbonate, zirconium potassium carbonate, zirconium sulfate,and zirconium fluoride. In particular, zirconium acetate can be used.Examples of the zirconium acetate include Zircosol ZA-30 (manufacturedby Daiichi Kigenso Kagaku Kogyo Co., Ltd.). Examples of thewater-soluble salt of aluminum include poly(aluminum chloride)(manufactured by Taki Chemical Co., Ltd.), poly(aluminum hydroxide)(manufactured by Asada Chemical Industry Co., Ltd.), and HAP-25(manufactured by RIKENGREEN Co., Ltd.).

The amount of the polyvalent metal contained in the ink-receiving layercan be 0.1 parts by mass or more, in particular, 0.3 parts by mass ormore, based on 100 parts by mass of the gas-phase method silica from theviewpoint of the ozone resistance of an image, and can be 10 parts bymass or less, in particular, 5 parts by mass or less, based on 100 partsby mass of the gas-phase method silica from the viewpoints of theink-absorbing properties and the color development of an image.

Other Materials

In the present invention, the ink-receiving layer may contain othermaterials in addition to the above-described materials. Examples of suchadditional materials include pH adjusters, thickeners, fluiditymodifiers, antifoaming agents, foam inhibitors, surfactants, releaseagents, penetrants, color pigments, color dyes, fluorescent brighteningagents, ultraviolet absorbers, antioxidants, antiseptics, antifungalagents, water resistant additives, dye-fixing agents, hardening agents,and weather resistant materials.

Base

The base used in the recording medium of the present invention may beany base, and examples of usable base include paper such as fine paper,medium quality paper, coated paper, art paper, and cast-coated paper;synthetic paper; white plastic films; transparent plastic films;translucent plastic films; and resin-coated paper.

In order to achieve effective expression of the glossiness of an image,the base should have high barrier properties against the coatingsolution for forming the ink-receiving layer. Examples of such a baseinclude white plastic films opacified by pore-introduction throughaddition of a pigment such as titanium oxide or barium sulfate to, forexample, polyethylene terephthalate, polyvinyl chloride, polycarbonate,polyimide, polyacetate, polyethylene, polypropylene, or polystyrene; andresin-coated paper, i.e., base paper laminated with a thermosettingresin such as polyethylene or polypropylene.

In order to allow the recording medium to achieve image quality andtexture equivalent to those of silver halide photography, the base paperused as the base can be polyolefin resin-coated paper where at least thesurface on which the ink-receiving layer is provided is coated with apolyolefin resin, in particular, polyolefin resin-coated paper where theboth surfaces are coated with a polyolefin resin. The polyolefinresin-coated paper can have a ten-point average roughness, measured inaccordance with JIS-B0601, of 0.5 μm or less and a 60-degree specularglossiness, measured in accordance with JIS-Z-8741, of 25% or more and75% or less.

The resin-coated paper can have any thickness, for example, a thicknessof 25 μm or more and 500 μm or less. Resin-coated paper having athickness of not less than 25 μm can effectively prevent the rigidity ofthe recording medium from decreasing and can effectively preventoccurrence of disadvantages such as degradations in the feel and texturewhen the recording medium is touched and a reduction in opacity.Resin-coated paper having a thickness of 500 μm or less can effectivelyprevent an increase in rigidity of the recording medium to avoid causingdifficulty in handling and can smoothly feed paper in an ink-jetrecording apparatus. The resin-coated paper can have a thickness of 50μm or more and 300 μm or less. The resin coated paper can have any basisweight, for example, a basis weight of 25 g/m² or more and 500 g/m² orless.

Method of Producing Recording Medium

In the present invention, the recording medium may be produced by anymethod and can be produced, for example, by a method including a processof coating a base with a coating solution for an ink-receiving layer.The method of producing the recording medium will now be described.

Method of Producing Base

In the recording medium of the present invention, the base can beproduced by a common process of producing paper. Examples of thepapermaking machine include Fourdrinier paper machines, cylinder papermachines, drum paper machines, and twin wire paper machines.

The base of the recording medium of the present invention may be coatedwith a porous material, such as light calcium carbonate, heavy calciumcarbonate, alumina, silica, or silicate, by a size press process, whichis usually performed in papermaking. The coating may be performed by acommon coating process. Specific examples of such a process include acoating technology using a device such as a gate roll coater, sizepress, bar coater, blade coater, air-knife coater, roll coater, blushcoater, curtain coater, gravure coater, or spray equipment. Theresulting base may be subjected to calender treatment, thermocalendertreatment, or super calender treatment to smoothen the surface thereof.

Method of Forming Ink-Receiving Layer

In the recording medium of the present invention, an ink-receiving layercan be formed on a base, for example, by mixing gas-phase method silica,a binder, and optional other additives to prepare a coating solution,applying the coating solution onto the base, and drying it. In thepresent invention, two types of coating solutions are prepared. Thecoating solutions may be successively applied and dried (successivecoating) or may be simultaneously applied (simultaneous multilayercoating). Specifically, for example, an ink-receiving layer is formed byapplying onto a base a coating solution containing gas-phase methodsilica and a binder and (1) not containing any cationic polymer having asulfonyl group or (2) containing a considerably small amount of acationic polymer having a sulfonyl group, i.e., in an amount not higherthan 0.1 parts by mass based on 100 parts by mass of the gas-phasemethod silica; and further applying thereon a coating solutioncontaining gas-phase method silica, a binder, a cationic polymer havinga sulfonyl group, and glycol. Alternatively, the ink-receiving layer maybe formed by simultaneously applying onto a base a coating solutioncontaining gas-phase method silica and a binder and (1) not containingany cationic polymer having a sulfonyl group or (2) containing aconsiderably small amount of a cationic polymer having a sulfonyl group,i.e., in an amount not higher than 0.1 parts by mass based on 100 partsby mass of the gas-phase method silica and a coating solution containinggas-phase method silica, a binder, a cationic polymer having a sulfonylgroup, and glycol. In particular, simultaneous multilayer coating, suchas slide bead coating or slide curtain coating, shows high productivity.The coating amount of the coating solution can be 5 g/m² or more and 45g/m² or less in terms of dried solid content. An application amount of 5g/m² or more can provide good ink-absorbing properties. An applicationamount of 45 g/m² or less can prevent occurrence of cockling. After theformation of the ink-receiving layer, the surface of the recordingmedium may be smoothened by calender treatment, thermocalendertreatment, or super calender treatment.

EXAMPLES

The present invention will now be more specifically described byreference examples, examples, and comparative examples, but is notlimited by the following examples, within the scope of the presentinvention. In the following examples, the term “part(s)” is on a massbasis unless otherwise specified.

Reference Example 1 Production of Base

A base was produced under the following conditions. Paper stuff of thefollowing composition was prepared with water so as to have a solidcontent of 3 mass %.

Paper Stuff Composition:

Pulp  100 parts (80 parts of broadleaf tree bleached kraft pulp (LBKP)having a freeness of 450 mL CSF (Canadian Standard Freeness) and 20parts of needle-leaf bleached kraft pulp (NBKP) having a freeness of 480mL CSF) Cationized starch 0.60 parts Heavy calcium carbonate   10 partsLight calcium carbonate   15 parts Alkyl ketene dimer 0.10 partsCationic polyacrylamide 0.03 parts

The resulting paper stuff was formed into a sheet with a Fourdrinierpaper machine, and the sheet was subjected to three-stage wet pressing,followed by drying with a multi-cylinder dryer. The resulting sheet wasimpregnated with an aqueous oxidized starch solution in a coating amountof 1.0 g/m² using a size press apparatus and was dried, followed byfinishing with a machine calender to give base paper having a basisweight of 170 g/m², a stockigt sizing degree of 100 seconds, an airpermeability of 50 seconds, a Bekk smoothness of 30 seconds, and aGurley stiffness of 11.0 mN.

Onto the resulting base paper, a resin composition composed of 70 partsof low-density polyethylene, 20 parts of high-density polyethylene, and10 parts of titanium oxide was applied in an amount of 25 g/m². Onto theback surface of the base paper, a resin composition composed of 50 partsof high-density polyethylene and 50 parts of low-density polyethylenewas applied in an amount of 25 g/m² to give a resin-coated base.

Preparation of Gas-Phase Method Silica Sol A

To 79.23 parts of deionized water added was 1.54 parts ofpoly(diallyldimethylamine hydrochloride) (SHALLOL DC902P, manufacturedby Daiichi Kogyo Seiyaku Co., Ltd., solid content: 50 mass %). 19.23parts of gas-phase method silica (AEROSIL 300, manufactured by EVONIKIndustries A.G.) was gradually added to the resulting aqueous cationicpolymer solution (the amount of poly(diallyldimethylamine hydrochloride)is 4 parts by mass based on 100 parts by mass of gas-phase method silicain terms of solid content) with stirring with a T.K. homomixer (model:MARK II 2.5, manufactured by Tokusyu Kika Kogyo Co., Ltd.) at 3000 rpm.Furthermore, treatment with a Nanomizer (manufactured by Yoshida KikaiCo., Ltd.) was performed twice to prepare gas-phase method silica sol Ahaving a solid content of 20 mass %.

Preparation Binder Solution

Polyvinyl alcohol (PVA 235, manufactured by Kuraray Co., Ltd., viscosityaverage polymerization degree: 3500, saponification degree: 88 mol %)was dissolved in deionized water to give a binder solution having asolid content of 8.0 mass %.

Preparation of Coating Solution 1 for Ink-Receiving Layer

A cationic polymer having a sulfonyl group (diallyldimethylammoniumchloride-sulfur dioxide copolymer, PAS-A-5, manufactured by NittoboMedical Co., Ltd., solid content: 40 mass %), a water-soluble salt of apolyvalent metal (zirconium acetate, ZA-30, manufactured by DaiichiKigenso Kagaku Kogyo Co., Ltd., solid content: 30 mass %), and anaqueous binder solution were mixed with gas-phase method silica sol A inamounts of 1.0 part, 2.0 parts, and 20.0 parts, respectively, in termsof solid content, based on 100 parts of the gas-phase method silicasolid content contained in gas-phase method silica sol A to give amixture solution. Subsequently, a crosslinking agent (aqueous orthoboricacid solution, solid content: 5 mass %) was mixed with the resultingmixture solution in an amount of 20.0 parts, in terms of solid content,based on 100 parts of the polyvinyl alcohol solid content contained inthe mixture solution. Furthermore, a surfactant (Surfinol 465,manufactured by Nissin Chemical Co., Ltd.) was added thereto in anamount of 0.1 mass % based on the total mass of the coating solution togive coating solution 1 for ink-receiving layer.

Preparation of Coating Solution 2 for Ink-Receiving Layer

Coating solution 2 for ink-receiving layer was prepared as in“Preparation of coating solution 1 for ink-receiving layer” except thatcoating solution 2 did not contain the cationic polymer having asulfonyl group (diallyldimethylammonium chloride-sulfur dioxidecopolymer, PAS-A-5).

Production of Recording Medium

The coating solutions 1 and 2 for ink-receiving layer was applied ontothe base produced above to form a layer of coating solution 2 forink-receiving layer having a dried thickness of 40 μm and a layer ofcoating solution 1 for ink-receiving layer having a dried thickness of25 μm in this order from the base side with a multilayer slide hoppercoating machine, followed by drying at 60° C. to produce a recordingmedium of Reference Example 1.

Examples 1 to 3

Recording media of Examples 1 to 3 were produced as in Reference Example1 except that propylene glycol as the glycol was further mixed with thegas-phase method silica sol A in “Preparation of coating solution 1 forink-receiving layer” in Reference Example 1 in amounts of 2.0 parts,10.0 parts, and 20.0 parts, respectively, in terms of solid content,based on 100 parts of gas-phase method silica solid content contained inthe gas-phase method silica sol A.

Example 4

A recording medium of Example 4 was produced as in Reference Example 1except that ethylene glycol as the glycol was further mixed with thegas-phase method silica sol A in “Preparation of coating solution 1 forink-receiving layer” in Reference Example 1 in an amount of 10.0 parts,in terms of solid content, based on 100 parts of gas-phase method silicasolid content contained in the gas-phase method silica sol A.

Example 5

A recording medium of Example 5 was produced as in Reference Example 1except that 1,2-hexanediol as the glycol was further mixed with thegas-phase method silica sol A in “Preparation of coating solution 1 forink-receiving layer” in Reference Example 1 in an amount of 10.0 parts,in terms of solid content, based on 100 parts of gas-phase method silicasolid content contained in the gas-phase method silica sol A.

Example 6

A recording medium of Example 6 was produced as in Reference Example 1except that isopropanol was further mixed with the gas-phase methodsilica sol A in “Preparation of coating solution 1 for ink-receivinglayer” in Reference Example 1 in an amount of 10.0 parts, in terms ofsolid content, based on 100 parts of gas-phase method silica solidcontent contained in the gas-phase method silica sol A.

Example 7

A recording medium of Example 7 was produced as in Reference Example 1except that malonic acid was further mixed with the gas-phase methodsilica sol A in “Preparation of coating solution 1 for ink-receivinglayer” in Reference Example 1 in an amount of 10.0 parts, in terms ofsolid content, based on 100 parts of gas-phase method silica solidcontent contained in the gas-phase method silica sol A.

Example 8

A recording medium of Example 8 was produced as in Reference Example 1except that 1.0 part of a methyldiallylamine hydrochloride-sulfurdioxide copolymer (PAS-2201CL, manufactured by Nittobo Medical Co.,Ltd., solid content: 25 mass %) was used in place of 1.0 part of thecationic polymer having a sulfonyl group (diallyldimethylammoniumchloride-sulfur dioxide copolymer, PAS-A-5) in “Preparation of coatingsolution 1 for ink-receiving layer” in Reference Example 1.

Example 9

A recording medium of Example 9 was produced as in Reference Example 1except that 1.0 part of a diallylmethylethylammonium ethylsulfate-sulfurdioxide copolymer (PAS-2401, manufactured by Nittobo Medical Co., Ltd.,solid content: 25 mass %) was used in place of 1.0 part of the cationicpolymer having a sulfonyl group (diallyldimethylammonium chloride-sulfurdioxide copolymer, PAS-A-5) in “Preparation of coating solution 1 forink-receiving layer” in Reference Example 1.

Example 10

A recording medium of Example 10 was produced as in Reference Example 1except that 1.0 part of a diallylamine hydrochloride-sulfur dioxidecopolymer (PAS-92, manufactured by Nittobo Medical Co., Ltd., solidcontent: 20 mass %) was used in place of 1.0 part of the cationicpolymer having a sulfonyl group (diallyldimethylammonium chloride-sulfurdioxide copolymer, PAS-A-5) in “Preparation of coating solution 1 forink-receiving layer” in Reference Example 1.

Examples 11 to 14

Recording media of Examples 11 to 14 were produced as in ReferenceExample 1 except that the amounts of the cationic polymer having asulfonyl group (diallyldimethylammonium chloride-sulfur dioxidecopolymer, PAS-A-5) in “Preparation of coating solution 1 forink-receiving layer” in Reference Example 1 were 0.2 parts, 0.5 parts,2.0 parts, and 4.0 parts, respectively.

Example 15

A recording medium of Example 15 was produced as in Example 2 exceptthat the coating solutions 1 and 2 for ink-receiving layer were appliedto form layers having dried thicknesses of 5 μm and 35 μm, respectively,in “Production of recording medium” in Example 2.

Example 16

A recording medium of Example 16 was produced as in Example 2 exceptthat the coating solutions 1 and 2 for ink-receiving layer were appliedto form layers having dried thicknesses of 10 μm and 30 μm,respectively, in “Production of recording medium” in Example 2.

Example 17

A recording medium of Example 17 was produced as in Example 2 exceptthat the coating solutions 1 and 2 for ink-receiving layer were appliedto form layers having dried thicknesses of 25 μm and 15 μm,respectively, in “Production of recording medium” in Example 2.

Example 18

A recording medium of Example 18 was produced as in Example 2 exceptthat the coating solutions 1 and 2 for ink-receiving layer were appliedto form layers having dried thicknesses of 30 μm and 10 μm,respectively, in “Production of recording medium” in Example 2.

Example 19

A recording medium of Example 19 was produced as in Example 2 exceptthat a coating solution composed of colloidal silica (Quotron PL-3L,manufactured by Fuso Chemical Co., Ltd., solid content: 20%) and highlybasic poly(aluminum chloride) (HAP25, manufactured by RIKENGREEN Co.,Ltd., solid content: 25%) at a solid content mass ratio of 100:10 wasfurther coated on the recording medium produced in Example 2 to form alayer having a dried thickness 0.2 μm using a bar coater.

Example 20

A recording medium of Example 20 was produced as in Reference Example 1except that propylene glycol as the glycol was further added to thegas-phase method silica sol A in “Preparation of coating solution 1 forink-receiving layer” in Reference Example 1 in an amount of 10.0 parts,in terms of solid content, based on 100 parts of gas-phase method silicasolid content contained in the gas-phase method silica sol A and that acationic polymer having a sulfonyl group (diallyldimethylammoniumchloride-sulfur dioxide copolymer, PAS-A-5) was further added to thegas-phase method silica sol A in “Preparation of coating solution 2 forink-receiving layer” in an amount of 0.1 part, in terms of solidcontent, based on 100 parts of gas-phase method silica solid content.

Comparative Example 1

A recording medium of Comparative Example 1 was produced as in ReferenceExample 1 except that the cationic polymer having a sulfonyl group(diallyldimethylammonium chloride-sulfur dioxide copolymer, PAS-A-5) in“Preparation of coating solution 1 for ink-receiving layer” in ReferenceExample 1 was not used.

Comparative Example 2

A recording medium of Comparative Example 2 was produced as in Example 2except that the cationic polymer having a sulfonyl group(diallyldimethylammonium chloride-sulfur dioxide copolymer, PAS-A-5) in“Preparation of coating solution 1 for ink-receiving layer” in Example 2was not used.

Comparative Example 3

A recording medium of Comparative Example 3 was produced as inComparative Example 1 except that a layer of coating solution 1 forink-receiving layer and a layer of coating solution 2 for ink-receivinglayer were formed in this order from the base side so as to have driedthicknesses of 25 μm and 15 μm, respectively, in “Production ofrecording medium” in Reference Example 1.

Comparative Example 4

A recording medium of Comparative Example 4 was produced as in Example 9except that a layer of coating solution 1 for ink-receiving layer and alayer of coating solution 2 for ink-receiving layer were formed in thisorder from the base side so as to have dried thicknesses of 25 μm and 15μm, respectively, in “Production of recording medium” in Example 9.

Comparative Example 5

A recording medium of Comparative Example 5 was produced as in Example 2except that a layer of coating solution 1 for ink-receiving layer and alayer of coating solution 2 for ink-receiving layer were formed in thisorder from the base side so as to have dried thicknesses of 25 μm and 15μm, respectively, in “Production of recording medium” in Example 2.

Comparative Example 6

A recording medium of Comparative Example 6 was produced as in Example 2except that two layers of coating solution 1 for ink-receiving layerwere formed so as to have dried thicknesses of 25 μm and 15 μm in thisorder from the base side in “Production of recording medium” in Example2.

Comparative Example 7

A recording medium of Comparative Example 7 was produced as in Example 2except that 1.0 part of a cationic polymer not having a sulfonyl group(poly(diallyldimethylamine hydrochloride), Shallol DC902P, manufacturedby Daiichi Kogyo Seiyaku Co., Ltd., solid content: 50 mass %) was usedin place of 1.0 part of the cationic polymer having a sulfonyl group(diallyldimethylammonium chloride-sulfur dioxide copolymer, PAS-A-5) in“Preparation of coating solution 1 for ink-receiving layer” in Example2.

Comparative Example 8

A recording medium of Comparative Example 8 was produced as in Example 2except that 1.0 part of a cationic polymer not having a sulfonyl group(poly(allylamine hydrochloride), PAA-HCL-05, manufactured by NittoboMedical Co., Ltd., solid content: 40 mass %) was used in place of 1.0part of the cationic polymer having a sulfonyl group(diallyldimethylammonium chloride-sulfur dioxide copolymer, PAS-A-5) in“Preparation of coating solution 1 for ink-receiving layer” in Example2.

Comparative Example 9

A recording medium of Comparative Example 9 was produced as in Example 2except that 1.0 part of a cationic polymer not having a sulfonyl group(poly(methyldiallylamine), PAS-M-1, manufactured by Nittobo Medical Co.,Ltd., solid content: 50 mass %) was used in place of 1.0 part of thecationic polymer having a sulfonyl group (diallyldimethylammoniumchloride-sulfur dioxide copolymer, PAS-A-5) in “Preparation of coatingsolution 1 for ink-receiving layer” in Example 2.

Comparative Example 10

A recording medium of Comparative Example 10 was produced as in Example2 except that 1.0 part of a cationic polymer not having a sulfonyl group(diallyldimethylammonium chloride-acrylamide copolymer, PAS-J-81,manufactured by Nittobo Medical Co., Ltd., solid content: 25 mass %) wasused in place of 1.0 part of the cationic polymer having a sulfonylgroup (diallyldimethylammonium chloride-sulfur dioxide copolymer,PAS-A-5) in “Preparation of coating solution 1 for ink-receiving layer”in Example 2.

Table 1 shows the compositions of ink-receiving layers of the recordingmedia produced above. The abbreviations in Table 1 are as those shown inthe description of the method of producing each recording medium.

TABLE 1 Composition of ink-receiving layer of recording medium Secondlayer adjacent to support Cationic polymer Glycols, etc. First layer notadjacent to support Thickness Content Content Thickness Cationic polymerExample No. (μm) Type (parts by mass) Type (parts by mass) (μm) TypeExample 1 25 — — — — 15 PAS-A-5 Example 2 25 — — — — 15 PAS-A-5 Example3 25 — — — — 15 PAS-A-5 Example 4 25 — — — — 15 PAS-A-5 Example 5 25 — —— — 15 PAS-A-5 Example 6 25 — — — — 15 PAS-A-5 Example 7 25 — — — — 15PAS-A-5 Example 8 25 — — — — 15 PAS-2201CL Example 9 25 — — — — 15PAS-2401 Example 10 25 — — — — 15 PAS-92 Example 11 25 — — — — 15PAS-A-5 Example 12 25 — — — — 15 PAS-A-5 Example 13 25 — — — — 15PAS-A-5 Example 14 25 — — — — 15 PAS-A-5 Example 15 35 — — — — 5 PAS-A-5Example 16 30 — — — — 10 PAS-A-5 Example 17 15 — — — — 25 PAS-A-5Example 18 10 — — — — 30 PAS-A-5 Example 19 25 — — — — 15 PAS-A-5Example 20 25 PAS-A-5 0.1 — — 15 PAS-A-5 Comp. Ex. 1 25 — — — — 15 —Comp. Ex. 2 25 — — — — 15 — Comp. Ex. 3 25 PAS-A-5 1.0 — — 15 — Comp.Ex. 4 25 PAS-A-5 1.0 propylene glycol 10.0 15 — Comp. Ex. 5 25 PAS-921.0 propylene glycol 10.0 15 — Comp. Ex. 6 25 PAS-A-5 1.0 propyleneglycol 10.0 15 PAS-A-5 Comp. Ex. 7 25 — — — — 15 DC-902P Comp. Ex. 8 25— — — — 15 PAA-HCl-05 Comp. Ex. 9 25 — — — — 15 PAS-M-1 Comp. Ex. 10 25— — — — 15 PAS-J-81 First layer not adjacent to support Cationic polymerGlycols, etc. Third layer Content Content Thickness Example No. (partsby mass) Type (parts by mass) (μm) Type Example 1 1.0 propylene glycol 2.0 — — Example 2 1.0 propylene glycol 10.0 — — Example 3 1.0 propyleneglycol 20.0 — — Example 4 1.0 ethylene glycol 10.0 — — Example 5 1.01,2-hexanediol 10.0 — — Example 6 1.0 isopropanol 10.0 — — Example 7 1.0malonic acid 10.0 — — Example 8 1.0 propylene glycol 10.0 — — Example 91.0 propylene glycol 10.0 — — Example 10 1.0 propylene glycol 10.0 — —Example 11 0.2 propylene glycol 10.0 — — Example 12 0.5 propylene glycol10.0 — — Example 13 2.0 propylene glycol 10.0 — — Example 14 4.0propylene glycol 10.0 — — Example 15 1.0 propylene glycol 10.0 — —Example 16 1.0 propylene glycol 10.0 — — Example 17 1.0 propylene glycol10.0 — — Example 18 1.0 propylene glycol 10.0 — — Example 19 1.0propylene glycol 10.0 0.2 PL-3L/HAP25 Example 20 1.0 propylene glycol10.0 — — Comp. Ex. 1 — — — — — Comp. Ex. 2 — propylene glycol 10.0 — —Comp. Ex. 3 — — — — — Comp. Ex. 4 — — — — — Comp. Ex. 5 — — — — — Comp.Ex. 6 1.0 propylene glycol 10.0 — — Comp. Ex. 7 1.0 propylene glycol10.0 — — Comp. Ex. 8 1.0 propylene glycol 10.0 — — Comp. Ex. 9 1.0propylene glycol 10.0 — — Comp. Ex. 10 1.0 propylene glycol 10.0 — —Evaluation

In the present invention, A to C in the evaluation criteria of eachevaluation item are acceptable levels, and D and E are unacceptablelevels. Incidentally, each evaluation was performed using an ink-jetrecording apparatus, PIXUS MP990 (manufactured by CANON KABUSHIKIKAISHA) equipped with an ink cartridge BCI-321 (manufactured by CANONKABUSHIKI KAISHA). The recording conditions were a temperature of 23° C.and a relative humidity of 50%. In the ink-jet recording apparatus, animage recorded under conditions of a resolution of 600×600 dpi andapplication of one ink drop of about 11 ng to a unit region of 1/600×1/600 inch is defined as a recording duty of 100%.

Effect of Inhibiting Cracking of Ink-Receiving Layer

The ink-receiving layer surface of each recording media produced abovewas visually observed to evaluate the effect of inhibiting cracking ofthe ink-receiving layer. The evaluation criteria are as follows:

A: no cracking was observed,

B: slight cracking was observed,

C: though cracking partially occurred, but it was not noticeable,

D: cracking was observed in the whole area, and

E: large cracking was observed, and the ink-receiving layer partiallydetached from the base.

The evaluation results are shown in Table 2.

Ozone Resistance of Image

A black patch (2.5×2.5 cm) was recorded on each recording mediumproduced above at an optical density of 1.0±0.1 using the ink-jetrecording apparatus set to the mode of “luster pro platinum grade”. Theresulting image was placed in an ozone exposure tester OMS-H(manufactured by Suga Test Instruments Co., Ltd.) and was exposed to 2.5ppm of ozone at a temperature of 23° C. and a relative humidity of 50%for 100 hours. The optical densities of the black patch before and afterthe exposure test were measured with a spectrophotometer Spectrolino(manufactured by Gretag Macbeth A.G.), and the density residual ratio ofeach of the cyan, magenta, and yellow components was calculated by thefollowing Expression:Density residual ratio(%)=(image density after test/image density beforetest)×100The ozone resistance of each image was evaluated on the basis of thedensity residual ratio of the cyan component, which was judged, from thedensity residual ratios, to be mostly affected by ozone. Incidentally, alarger density residual ratio means higher ozone resistance of an image.The evaluation criteria are as follows:

A: the density residual ratio of cyan component was 82% or more,

B: the density residual ratio of cyan component was 79% or more and lessthan 82%,

C: the density residual ratio of cyan component was 76% or more and lessthan 79%,

D: the density residual ratio of cyan component was 73% or more and lessthan 76%, and

E: the density residual ratio of cyan component was less than 73%.

The evaluation results are shown in Table 2.

Bronze Resistance of Image

A cyan solid image (an image of a recording duty of 100%) of 2.5×2.5 cmwas recorded on each recording medium produced above using the ink-jetrecording apparatus set to the mode of “luster pro platinum grade, nocolor correction”. The bronze resistance of the resulting image wasevaluated by visually observing the image. The evaluation criteria areas follows:

A: no bronze was observed,

B: very slight reddish bronze was observed,

C: slight reddish bronze was observed, but it was not noticeable,

D: reddish bronze was observed, and

E: metallic luster bronze was observed.

The evaluation results are shown in Table 2.

Effect of inhibiting heat-induced yellowing of recording medium

Each recording medium produced above was stored under high temperatureconditions, a temperature of 90° C. and a relative humidity of 50%, for48 hours. The blank portion of the recording medium was measured for theL* values, a* values, and b* values before and after the storage testwith a spectrophotometer Spectrolino (manufactured by Gretag MacbethA.G.), and ΔE was calculated by the following Expression:ΔE=[{(L*value of recorded matter before test)−(L*value of recordedmatter after test)}²+{(a*value of recorded matter before test)−(a*valueof recorded matter after test)}²+{(b*value of recorded matter beforetest)−(b*value of recorded matter after test)}²]^(1/2)The effect of inhibiting the heat-induced yellowing of the recordingmedium was evaluated from the resulting ΔE. Incidentally, a smaller ΔEmeans that the heat-induced yellowing of the recording medium is moreinhibited. The evaluation criteria are as follows:

A: ΔE was less than 2.3,

B: ΔE was 2.3 or more and less than 2.6,

C: ΔE was 2.6 or more and less than 2.9,

D: ΔE was 2.9 or more and less than 3.2, and

E: ΔE was 3.2 or more.

The evaluation results are shown in Table 2.

TABLE 2 Evaluation results Effect of Effect of inhibiting inhibitingcracking Ozone Bronze heat-induced of ink- resistance resistanceyellowing of Example No. receiving layer of image of image recordingmedium Example 1 A A C A Example 2 A A A A Example 3 C A A A Example 4 BA A A Example 5 C A A A Example 6 B A C A Example 7 C A C A Example 8 AA A A Example 9 A A A A Example 10 A A A C Example 11 B C A A Example 12B B A A Example 13 B A B A Example 14 A A C A Example 15 A C A A Example16 A B A A Example 17 B A A A Example 18 C A A A Example 19 A A A AExample 20 A A A A Comparative A E A A Example 1 Comparative A E A AExample 2 Comparative D D B A Example 3 Comparative E D A A Example 4Comparative E D A D Example 5 Comparative E A A A Example 6 ComparativeA D D A Example 7 Comparative A D C E Example 8 Comparative A D C AExample 9 Comparative A D C A Example 10

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the invention is notlimited to the disclosed exemplary embodiments. The scope of thefollowing claims is to be accorded the broadest interpretation so as toencompass all such modifications and equivalent structures andfunctions.

This application claims the benefit of Japanese Patent Application No.2012-086534 filed Apr. 5, 2012, which is hereby incorporated byreference herein in its entirety.

What is claimed is:
 1. A recording medium comprising a base, a secondink-receiving layer, and a first ink-receiving layer in this order,wherein the first ink-receiving layer comprises gas-phase method silica,a binder, a cationic polymer having a sulfonyl group, and glycol; andthe second ink-receiving layer comprises gas-phase method silica and abinder and (1) does not comprise any cationic polymer having a sulfonylgroup or (2) comprises a cationic polymer having a sulfonyl group in anamount not higher than 0.1 parts by mass based on 100 parts by mass ofthe gas-phase method silica.
 2. The recording medium according to claim1, wherein the content of the glycol in the first ink-receiving layer is2.0 parts by mass or more and 20.0 parts by mass or less based on 100parts by mass of the cationic polymer having a sulfonyl group.
 3. Therecording medium according to claim 1, wherein the cationic polymerhaving a sulfonyl group comprises a compound represented by thefollowing Formula (1):

(in Formula (1), R₁ and R₂ each represent a hydrogen atom or an alkylgroup, provided that R₁ and R₂ are not simultaneously hydrogen atoms; X⁻represents a halogen ion, a sulfate ion, a sulfonate ion, analkylsulfonate ion, an acetate ion, an alkylcarboxylate ion, or aphosphate ion; and n is an integer).
 4. The recording medium accordingto claim 1, wherein the content of the cationic polymer having asulfonyl group in the first ink-receiving layer is 0.2 parts by mass ormore and 4.0 parts by mass or less based on 100 parts by mass of thegas-phase method silica.
 5. The recording medium according to claim 1,wherein the content of the glycol in the first ink-receiving layer is2.0 parts by mass or more and 20.0 parts by mass or less based on 100parts by mass of the gas-phase method silica.
 6. A method of producing arecording medium according to claim 1, the method comprising: applyingonto a base a coating solution containing gas-phase method silica and abinder and (1) not containing any cationic polymer having a sulfonylgroup or (2) containing a cationic polymer having a sulfonyl group in anamount not higher than 0.1 parts by mass based on 100 parts by mass ofthe gas-phase method silica; and applying onto the applied coatingsolution another coating solution containing gas-phase method silica, abinder, a cationic polymer having a sulfonyl group, and glycol.
 7. Amethod of producing a recording medium according to claim 1, the methodcomprising: simultaneously applying two coating solutions onto a base,wherein one coating solution contains gas-phase method silica and abinder and (1) does not contain any cationic polymer having a sulfonylgroup or (2) contains a cationic polymer having a sulfonyl group in anamount not higher than 0.1 parts by mass based on 100 parts by mass ofthe gas-phase method silica; and the other coating solution containsgas-phase method silica, a binder, a cationic polymer having a sulfonylgroup, and glycol.